Despite the ongoing efforts on energy efficiency improvements,, the lower energy consumption per data centre does not compensate the cumulative increasing energy demand, due to the combined action of increasing load density in the computer room and rising digitization of human activities. Hence data centres are consuming increasing amount of energy, with a negative impact on the environment and on power supply continuity. The GEYSER project aims to step well beyond today's Green data centres sustainability efforts by researching and delivering an innovative conceptual and software framework aimed at improving and trading-off local energy efficiency and carbon reduction footprint against a broader system-level smart city energy efficiency, while maximizing the use of renewable energy. GEYSER will originally combine innovative AC/DC data center optimized design practices with real time smart synergistic IT infrastructure (computing, storage), cooling and power subsystems for energy monitoring and control, with flexible supply/demand load and energy management within green energy-led marketplaces and geographical renewable energy supply-aware load balancing. GEYSER future green networked data centres will be able to monitor, control, reuse and optimize their energy consumption and production, from renewable energy in particular, within the framework of a holistic representation of energy (either power or heat) and along the underway roadmap towards acting as energy prosumers. Expected outcomes will be beyond-SoTA values for energy efficiency metrics, i.e PUE below 1,20 and CUE and ERE improvement by 30% in average. The effectiveness of the GEYSER technologies in meeting the planned objectives will be proved through a two-stage validation process, consisting of a simulation-based lab trial, followed by a real life one year validation in four operational data centres, partially powered by renewable energy, located in Italy, Germany and The Netherlands